#609 re-introduce PHPStan checking of the `PhpStormStubsSourceStubber` once PHPStan 0.12.26 is out

[Ocramius]

See #609 (we need to revert it once upstream is released)

[kukulich]

PHPStan 0.12.26 is out but it reports strange errors. Some have to be fixed in other libraries:

• Fixed Reflection*::export() @return annotations JetBrains/phpstorm-stubs#821
• Fixed parsing description started with HTML tag phpstan/phpdoc-parser#47

[kukulich]

Fixed in #760